"DW downunder" noname wrote

Perhaps a little more depth would help me understand - as I understand
you, with supercapacitors, emerging lithium technologies and our old
faithful lead-acid gel we haven't yet got a package of technologies that
can be tuned to the precise characteristics of suburban/interurban rail

It would be daft to develop Crossrail in the hope that adequate battery
technology would be available by the time the trains have to be ordered.
However, battery trains have been used for suburban rail - Dublin to Bray
between 1932 and 1950. In .uk a battery MU operated between Aberdeen and
Ballater in the early 1960s, while battery locos have been used to haul
engineering trains on LU in the dead of night when the power's een switched
off.

Peter